Chronic localized back pain due to entrapment of cutaneous branches of posterior rami of the thoracic nerves (POCNES): a case series on diagnosis and management

Introduction and aim

Chronic back pain (CBP) may be caused by a variety of conditions including dysfunctional muscles, ligaments or intervertebral discs, improper movement of vertebral column joints, or nerve root compression. Recently, CBP was treated successfully in a patient having an entrapment of cutaneous branches of the posterior rami of the thoracic nerves, termed posterior cutaneous nerve entrapment syndrome (POCNES). Our aim is to describe clinical presentation, differential diagnosis, and management of patients with such a neuropathic pain syndrome.

Methods

This study analyzed prospectively obtained data from consecutive patients suspected of having POCNES, presenting to two Dutch hospitals between January 2013 and September 2016. Patients received a diagnostic 2–5 mL 1% lidocaine injection just below the thoracolumbar fascia. Pain was scored using a numerical rating scale (0 = no pain to 10 = worst possible pain). A >50% pain reduction was defined as success. A neurectomy was proposed if pain reduction was temporary or insufficient after one to three injections. Long-term treatment effect was determined using a verbal rating scale (VRS; 1 = very satisfied, no pain, to 5 = pain worse).

Results

Fourteen patients (12 women, median age 26, age range 18–73) were diagnosed with POCNES. Eighty-one percent (n=11) reported a >50% pain drop after injection (NRS pain scores of median 8.0 [IQR 7.0–8.0] to median 3.0 [IQR 1.5–3.5], P<0.001). In one patient, repeated injections were successful long-term (VRS score of 2). Two patients declined surgery, whereas the remaining eleven underwent a neurectomy that was successful in seven (64%). A 57% long-term efficacy (median 29 months follow-up, range 5–48, VRS score 1–2) was attained in the entire study population.

Conclusion

POCNES should be considered in the differential diagnosis of chronic localized back pain. A treatment regimen including injections and neurectomy of the specific cutaneous branch results in long-term pain relief in more than half of these patients.

Adding steroids to lidocaine in a therapeutic injection regimen for patients with abdominal pain due to anterior cutaneous nerve entrapment syndrome (ACNES): a single blinded randomized clinical trial

Background and aims

Anterior cutaneous nerve entrapment syndrome (ACNES) may result in chronic abdominal pain. Therapeutic options include local injection therapy. Data on the efficacy of adding corticosteroids to these injections is lacking.

Methods

Patients ≥18 years with ACNES were randomized to receive an injection of lidocaine with (LC-group) or without (LA-group) the addition of methylprednisolone into the point of maximal abdominal wall pain. Pain was recorded using a numeric rating scale (NRS: 0–10) and a verbal rating scale (VRS: 0=no pain, 5=unbearable pain) at baseline and 6 weeks after the start of a bi-weekly injection regimen consisting of a total of three injections. A minimal 50% reduction on NRS and/or two points on VRS were considered successful responses.

Results

Between February 2014 and August 2016, 136 patients (median age 46 year, range 18–79, 75% females) were randomized (68 vs. 68). The proportion of patients demonstrating a successful response after 6 weeks did not significantly differ between groups (LA 38%, LC 31%, p=0.61). At 12 weeks, the number of patients still experiencing a minimal 50% pain relief had decreased but no group difference was observed (LA 20%, LC 18%, p=0.80). Minor side effects included temporary increase of pain, tenderness at injection sites or transient malaise (LA23/68, LC 29/68, p=0.46).

Conclusions

Adding corticosteroids to a lidocaine does not increase the proportion of ACNES patients with a successful response to injection therapy. Lidocaine alone can provide long term pain relief after one or multiple injections, in approximately 1 of 5 patients.

Treatment response and central pain processing in Anterior Cutaneous Nerve Entrapment Syndrome: An explorative study

BACKGROUND

10-30% of chronic abdominal pain originates in the abdominal wall. A common cause for chronic abdominal wall pain is the Anterior Cutaneous Nerve Entrapment Syndrome (ACNES), in which an intercostal nerve branch is entrapped in the abdominal rectus sheath. Treatment consists of local anaesthetics and neurectomy, and is ineffective in 25% of cases for yet unknown reasons. In some conditions, chronic pain is the result of altered pain processing. This so-called sensitization can manifest as segmental or even generalized hyperalgesia, and is generally difficult to treat.

OBJECTIVE

The aim of this study was to assess pain processing in ACNES patients responsive and refractory to treatment by using Quantitative Sensory Testing, in order to explore whether signs of altered central pain processing are present in ACNES and are a possible explanation for poor treatment outcomes.

METHODS

50 patients treated for ACNES with locally orientated treatment were included. They were allocated to a responsive or refractory group based on their response to treatment. Patients showing an improvement of the Visual Analogue Scale (VAS) pain score combined with a current absolute VAS of <40mm were scored as responsive. Sensation and pain thresholds to pressure and electric skin stimulation were determined in the paravertebral bilateral ACNES dermatomes and at four control areas on the non-dominant side of the body, i.e. the musculus trapezius pars medialis, musculus rectus femoris, musculus abductor hallucis and the thenar. The ACNES dermatomes were chosen to signal segmental hyperalgesia and the sum of the control areas together as a reflection of generalized hyperalgesia. Lower thresholds were interpreted as signs of sensitized pain processing. To test for alterations in endogenous pain inhibition, a conditioned pain modulation (CPM) response to a cold pressor task was determined. Also, patients filled in three pain-related questionnaires, to evaluate possible influence of psychological characteristics on the experienced pain.

RESULTS

Patients refractory to treatment showed significantly lower pressure pain thresholds in the ACNES dermatomes and for the sum of as well as in two individual control areas. No differences were found between groups for electric thresholds or CPM response. Duration of complaints before diagnosis and treatment was significantly longer in the refractory compared to the responsive group, and refractory patients scored higher on the pain-related psychological surveys.

CONCLUSION AND IMPLICATIONS

In this hypothesis-generating exploratory study, ACNES patients refractory to treatment showed more signs of sensitized segmental and central pain processing. A longer duration of complaints before diagnosis and treatment may be related to these alterations in pain processing, and both findings could be associated with less effective locally orientated treatment. In order to validate these hypotheses further research is needed.

REGISTRATION NUMBER

NCT01920880 (Clinical Trials Register; http://www.clinicaltrials.gov).

Chronic Localized Back Pain Due to Posterior Cutaneous Nerve Entrapment Syndrome (POCNES): A New Diagnosis

Most patients with chronic back pain suffer from degenerative thoracolumbovertebral disease. However, the following case illustrates that a localized peripheral nerve entrapment must be considered in the differential diagnosis of chronic back pain. We report the case of a 26-year-old woman with continuous excruciating pain in the lower back area. Previous treatment for nephroptosis was to no avail. On physical examination the pain was present in a 2 x 2 cm area overlying the twelfth rib some 4 cm lateral to the spinal process. Somatosensory testing using swab and alcohol gauze demonstrated the presence of skin hypo- and dysesthesia over the painful area. Local pressure on this painful spot elicited an extreme pain response that did not irradiate towards the periphery. These findings were highly suggestive of a posterior version of the anterior cutaneous nerve entrapment syndrome (ACNES), a condition leading to a severe localized neuropathic pain in anterior portions of the abdominal wall. She demonstrated a beneficial albeit temporary response after lidocaine infiltration as dictated by an established diagnostic and treatment protocol for ACNES. She subsequently underwent a local neurectomy of the involved superficial branch of the intercostal nerve. This limited operation had a favorable outcome resulting in a pain-free return to normal activities up to this very day (follow-up of 24 months).We propose to name this novel syndrome "posterior cutaneous nerve entrapment syndrome" (POCNES). Each patient with chronic localized back pain should undergo simple somatosensory testing to detect the presence of overlying skin hypo- and dysesthesia possibly reflecting an entrapped posterior cutaneous nerve.Key words: Chronic pain, back pain, posterior cutaneous nerve entrapment, peripheral nerve entrapment, surgical treatment for pain, anterior cutaneous nerve entrapment.

Surgical options after a failed neurectomy in anterior cutaneous nerve entrapment syndrome

BACKGROUND

Injection treatment followed by an anterior neurectomy in patients insufficiently responding to an injection regimen is successful long term in three-quarters of patients with anterior cutaneous nerve entrapment syndrome (ACNES). The efficacy of secondary surgery, including re-exploration or a posterior neurectomy in patients reporting recurrent pain after initially successful surgery or following an immediately failed anterior neurectomy is unknown.

METHODS

A database of ACNES patients receiving surgery between 2004 and 2012 in the SolviMáx institution was analysed. Adult patients with residual pain after an anterior neurectomy (failures) or with recurrent pain after initially successful surgery (recurrences) were selected. Following a re-exploration or a posterior neurectomy, pain was scored using a pain intensity numeric rating scale (PI-NRS 0-10) and a six-point verbal category rating scale (VRS). Success was defined as a ≥50 % PI-NRS reduction and/or ≥2 point VRS reduction.

RESULTS

ACNES patients undergoing an anterior neurectomy (n = 181) were analysed during the 8-year study period. At follow-up, 51 patients reported unacceptable pain levels following an anterior neurectomy, whereas 20 developed recurrent abdominal wall pain. Of these 71 unsuccessful patients, 41 underwent secondary surgery, including a re-exploration (n = 10), or a posterior neurectomy (n = 31). After a 25-month median follow-up, secondary surgical treatment regimens proved successful in 66 % (27/41). Patients with recurrent pain did better (14/15) than patients who were immediate failures after the anterior neurectomy (13/26, p = 0.01).

CONCLUSIONS

Secondary surgery including re-explorations and posterior neurectomies are successful in two-thirds of ACNES patients with persistent pain or recurrence of pain after an anterior neurectomy.

Long-term success rates after an anterior neurectomy in patients with an abdominal cutaneous nerve entrapment syndrome

BACKGROUND

Surgery occasionally is proposed in patients with chronic abdominal wall pain caused by an anterior cutaneous nerve entrapment syndrome (ACNES) who are refractory to injection therapy. An anterior neurectomy may seem successful, but follow-up is usually short and populations are small. The primary aim of this study was to determine the long-term success rate of surgery in a large ACNES population.

METHODS

In this retrospective observational study, patients with ACNES ≥18 years who underwent a primary anterior neurectomy between January 2004 and February 2012 in one single center were studied. Pain scores were obtained before surgery, after surgery, and at the moment of questioning using a pain intensity numeric rating scale (PI-NRS 0-10) and a 6-point verbal category rating scale. Success was defined as a ≥50% PI-NRS reduction or ≥2 point verbal rating scale reduction.

RESULTS

Data of 181 neurectomies in 154 individuals were available for analysis (female, n = 127, 82.5%; age 47 ± 17 years, range, 20-83). Pain before operation was severe (mean PI-NRS 8.08, SD 1.43). Short-term (1-3 months postoperative) success was 70% (127/181 procedures). Three subjects showed spontaneous remission of complaints after ≥3 months. After a mean 32 months (range, 3-93) follow-up, a success rate of 61% (109/180) on the long-term was found.

CONCLUSION

A 70% short-term success rate and a 61% long-term success rate after a primary anterior neurectomy in patients with chronic abdominal pain due to ACNES were attained. Surgery is the method of choice in ACNES patients who are refractory to a conservative regimen.

Construction and validation of a questionnaire distinguishing a chronic abdominal wall pain syndrome from irritable bowel syndrome

OBJECTIVE

The irritable bowel syndrome (IBS) population is heterogeneous, harbouring a variety of abdominal symptoms. Therefore, IBS is often termed a 'diagnosis of exclusion'. Chronic abdominal wall pain (CAWP) is a poorly recognized entity, frequently caused by the anterior cutaneous nerve entrapment syndrome (ACNES). Some patients may be misdiagnosed because IBS and CAWP share symptoms. Aim of this study was to construct and validate a questionnaire to distinguish patients with CAWP (including ACNES) patients with IBS.

DESIGN

A questionnaire was designed of 17 ACNES characteristic items obtained from ACNES patients (n=33) and expert opinion of two specialized surgeons. Eleven IBS-related items ('Rome III' criteria) were added leading to a questionnaire containing 28 items. This was validated in a 'gold standard' ACNES group (successfully operated ACNES patients, n=68) and a 'prospective' IBS group (n=64) as well as in a 'prospective' ACNES group (n=47). Distinctive power of individual items was analyzed by χ². Reliability was tested with Crohnbach's α. ROC curve was used to determine cut-off values.

RESULTS

Eighteen of 28 items were significantly distinctive (p<0.01) between ACNES and IBS patients leading to an 18-point ACNES score with good internal consistency (α=0.85). Cut-off value of 10 points resulted in 94% sensitivity, 92% specificity and areas under the curve (AUC) of 0.98. Evaluation of the prospective ACNES group led to 85% sensitivity, 92% specificity and AUC 0.95 indicating high discriminative properties of the questionnaire.

CONCLUSIONS

This novel questionnaire may be useful and valid as a simple tool distinguishing patients harbouring a CAWP syndrome from those having IBS.

Surgery for refractory anterior cutaneous nerve entrapment syndrome (ACNES) in children

BACKGROUND

Chronic abdominal pain (CAP) in children may be caused by entrapment of cutaneous branches of intercostal nerves (anterior cutaneous nerve entrapment syndrome, or ACNES). Local injection of anesthetics may offer relief, but pain is persistent in some children. This study is the first to describe the results of a 'cutaneous neurectomy' in children with refractory ACNES.

METHODS

Chronic abdominal pain children with suspected ACNES refractory to conservative treatment received a cutaneous neurectomy in a day care setting. They were interviewed postoperatively using an adapted quality of life questionnaire (testing quality of life in children).

RESULTS

All subjects (n = 6; median age, 15 years; range, 9-16 years) were previously healthy school-aged children without prior illness or earlier surgery. Each presented with intense abdominal pain and a positive Carnett sign. Blood, urine tests, and abdominal ultrasound investigations were normal. Delay in seeing a physician was 16 weeks, and school absence was 25 days. Before surgery, quality of life (pain, daily activities, and sports) was greatly diminished. After the neurectomy, all children were free of pain and had resumed their normal daily routine (follow-up at 6 months).

CONCLUSIONS

The role of the abdominal wall as the source of childhood CAP is underestimated. Some children with CAP have ACNES. Children with refractory ACNES should be offered a cutaneous neurectomy, as this simple technique is effective in the short and long term.